<div class="container-fluid third hidden-xs" id="b">
    <div class="carousel slide">
        <div class="carousel-inner">
            <div class="item active">
                <img src="__PUBLIC__/website/img/app2.png" alt="" width="100%"/>
            </div>
        </div>
    </div>
</div>
<div class="container-fluid third visible-xs" id="b">
    <div class="carousel slide">
        <div class="carousel-inner">
            <div class="item active">
                <img src="__PUBLIC__/website/img/app.png" alt="" style="width: 100%;"/>
            </div>
        </div>
    </div>
</div>